1. Field of the Invention
This invention relates to improvements in a fluid jet loom, and more particularly to an arrangement for automatically and effectively accomplishing a gaiting operation of the fluid jet loom without any troublesome manual operation.
2. Description of the Prior Art
In connection with an air jet loom, a gaiting operation for forming an initial rough structure of a woven fabric is carried out after a looming operation in which warp yarns on the loom are connected with new warp yarns from a replaced warp beam. The gaiting operation is usually carried out as follows: After the respective new warp yarns are connected automatically or manually with the new yarns, an inching switch button for starting an inching operation is pushed to rotate a loom main shaft in a normal direction, and then is released to stop rotation of the main shaft for example at a loom main shaft rotational angle of 180 degrees. At this timing of 180 degrees in loom main shaft rotational angle, air is ejected from a main nozzle and from some (a part) of auxiliary nozzles (as seen from a time chart of FIG. 2 in the present application). This is because during a normal weaving operation, electromagnetic valves for supplying the main and auxiliary nozzles with pressurized air are opened and closed at predetermined loom main shaft rotational angles; particularly the electromagnetic valves for the auxiliary nozzles are so operated that the auxiliary nozzles successively eject air in accordance with the flying position of the leading end of the picked weft yarn.
Subsequently by continuously pushing a measuring pawl releasing button provided in a weft measuring device, the weft yarn wound on a weft storing drum is released or disengaged from the measuring pawl and drawn from the drum to fly throughout a weft guide channel under the influence of an air jet from the main nozzle and from the some of the auxiliary nozzles, thereby accomplishing a weft picking. At this time, the length of the weft yarn unwound from the drum is visually observed. When the leading end of the picked weft yarn reaches a counter weft insertion side, an operator's finger is released from the measuring pawl releasing button to cause the measuring pawl to be again brought into contact with the weft storing drum to engage with the weft yarn on the drum.
The above gaiting operation is repeated until a predetermined tension is applied to warp yarns so that a weaving opeartion becomes stable. It will be understood that during the looming operation, the warp yarns are in a slackened condition, so that it is impossible to operate the loom. Accordingly, after repetition of the above gaiting operation, a loom starting switch button is pushed to start a normal weaving operation. Such a loom operation technique is disclosed, for example, in Japanese Utility Model Publication No. 58-113791, in which a loom is arranged to make its inching operation when an inching switch button is continued to be pushed under the action of a current supplying command device which is adapted to switch ON and OFF a driving circuit for a motor which drives the loom at predermined time intervals.
However, difficulties have encountered in the above-discussed arrangement as discussed hereinafter. At the weft picking during the gaiting operation, the loom main shaft is stopped at 180 degrees in loom main shaft rotational angle, and therefore air is ejected from only some of the auxiliary nozzles while ejecting air from the main nozzle. In other words, only a part of the auxiliary nozzles eject air, so that the remaining auxiliary nozzles cannot eject air. This makes the weft picking unstable, causing a mispick in which the picked weft yarn cannot reach the counter weft insertion side. Furthermore, disengagement and engagement operations of the measuring pawl to the weft yarn are manually carried out, and confirmation of the length of the picked weft yarn is visually made. Consequently, the length of the picked weft yarn is not uniform and causes an excess and deficiency in length, so that the weft yarn may become entangled with the warp yarns. In this case, the weft picking must be repeated many times after removing the entangled weft yarns, thus degrading an operational efficiency of the loom.